1. Field of the Invention
The present invention relates to a system and method of evaluating a magnetic property of a magnetic material. Particularly, the invention relates to an evaluating system and method for evaluating a magnetic property of a magnetoresistive device as a magnetic material.
2. Description of the Related Art
In recent years, with the rapid increase in recording density of a magnetic disc apparatus, a width of a magnetic recording area recorded on a medium, that is, a track width has become narrower. Therefore, it is important to evaluate a track width and its sensitivity distribution (distribution of intensity of magnetic field) in a reproducing device with a magnetic head, such as a magnetoresistive device.
Conventionally, estimation of the track width and measurement of the sensitivity distribution in the magnetoresistive device is carried out by detecting an output signal of the magnetic head reproducing element by making a signal from a medium recorded in a narrow track off track of the magnetic head reproducing device. Further, there is also a method of evaluating a magnetic property of the magnetoresistive device such that a hysteresis property is investigated by applying a magnetic field to an entire magnetoresistive device.
JP-A No.20929/2000 discloses a means of measuring a sensitivity distribution of a magnetic head, in which a magnetic force microscope is utilized. According to the apparatus, a probe bearing magnetism is oscillated and scanned with the oscillation above a magnetic head and a distribution of a reproduced sensitivity is measured from a change in an electric signal of a magnetoresistive device. Since an oscillating current produced by an oscillating magnetic field of a probe is detected, noise can be removed comparatively easily. Further, since a probe having a sharpened tip is used, there is also achieved an advantage that a spatial resolution is high. Further, since it is not necessary to move the magnetic head mechanically, the apparatus has a characteristic that an influence of a mechanical error of the system is inconsiderable compared to a conventional method or apparatus using an actual recording medium to estimate the property, which incurs mechanical error.
However, according to the method described in JP-A No.20929/2000, the probe is oscillated at a position spaced apart from a magnetic head sliding face by a constant distance and therefore, information of the sensitivity distribution is a relative value, and therefore the information is not an absolute value. Further, the method does not include correcting the relative value to the absolute value in JP-A NO.20929/2000 and therefore, there poses a problem that the quantative evaluation of the sensitivity distribution of the reproducing head cannot be realized, although the sensitivity can be evaluated qualitatively.
Further, since a magnetization state of the probe changes at respective measurement due to a disturbance by an external magnetic field and the magnetization state differ depending on the respective probe, a measured shape of the reproduced sensitivity distribution changes on each occasion, the measurement cannot have a sufficient reproducibility.